1. Field of the Invention
The present invention relates to a method for quantization of a histogram bin value of an image or video, and more particularly, to a method for non-uniform quantization of a color histogram bin value of an image (or video) according to the frequency of color occurrence.
2. Description of the Background Art
Conventionally, it is possible to reduce the amount of information for expressing a color histogram of an image if the color histogram bin value is quantized. However, the color histogram bin value is merely quantized uniformly, irrespective of the frequency of color occurrence in images.
FIG. 1 is a view illustrating an example of a table of uniform quantization of a color histogram bin value according to the conventional art. In other words, the color histogram bin value is quantized by partition into uniform intervals.
For example, when the color histogram bin value ranges from 0 to 1 and the bin value is expressed by 16 numbers of branch using 4-bits, it is quantized by partition into uniform sections of 0.0625 ( 1/16=0.0625).
However, the color histogram bin value is generally low in natural image (In FIG. 2, for example, there is almost no bin having a bin value of more than 0.1), particularly, bins having a bin value of 0 occupy the most part of the whole color histogram bins (In FIG. 2, for example, more than 95% of the whole color histogram bins).
Therefore, a color histogram bin value near to 0 has to be quantized finely by a large number so that the intervals of the bin value are small. In addition, a color histogram bin value near to 1 can be quantized coarsely by a small number so that the intervals of the bin value are large.
However, as described above, in the method for quantization of a color histogram bin value according to the conventional art, there arises a problem that the information of the color histogram is lost, since the color histogram is uniformly quantized irrespective of the frequency of the color histogram bin value.
For example, if the color histogram bin value is quantized without considering its characteristics, such as the existence or non-existence of a certain particular color in a certain image and the frequent occurrence or infrequent occurrence of a color in the image, the unique information of the color histogram, which is an important information as one of the characteristics of the image, cannot be precisely preserved.
In addition, since the unique information of the color histogram cannot be precisely preserved, it causes a problem that it is difficult for the information about quantization of color histogram bin value to obtain sufficient reliability in reflecting the characteristics of the image, where the information about quantization of color histogram bin value is usually used as a characteristic information of an image. In addition, if the information poorly reflecting the color histogram characteristics of the image is used, the performance of image searching is degraded for the image retrieval.
In addition, if the information poorly reflecting the color histogram characteristics of the image is used, there arises a problem that the image characteristics are not consistent with the visual/sensible characteristics of a human being.